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Abstract:

A method and device for determining the position of the object with a
light source. The light source illuminates light with a specific range of
wave length. The optical band-pass filter lets pass only the light from
the light source for the most part. And the camera only sees the light
from the light source which is mounted on the object. The arithmetic unit
calculates the position of the light source from the data of the cameras.
The position is known of the light source on the object and therefore it
is possible to determine the position of the object over the position of
the light source.

Claims:

1. Method for determining the position of a object (1;12;21) with light
source (2;13;22) through a light sensor/image sensor (5;17;25;32) with
optical band-pass filter (3;15;23;30), comprising the steps of: providing
a light sensor/image sensor (5;17;25;32), an optical band-pass filter
(3;15;23;30) set in front of a light sensor/image sensor (5;17;25;32), an
object (1;12;21) with a light source (2;13;22) and an arithmetic unit for
calculation the position of the object (1;12;21); the light source
(2;13;22) on the object (1;12;21) that illuminates light with a specific
range of wave length, the optical band-pass filter (3;15;23;30) let pass
only the light from the light source for the most part, therefore the
light sensor/image sensor (5;17;25;32) detect for the most part the light
from the light source (2;13;22) of the object (1;12;21), the arithmetic
unit calculate the position of the light source (2;13;22), the position
of the light source (2;13;22) on the object (1;12;21) is known and out of
it the arithmetic unit determine the position of the object (1;12;21).

3. Method according to claim 1, further comprising: one or more cameras
with optical band-pass filter, or one or more light sensors/image sensors
with optical band-pass filter, one or more light sources on the object, a
arithmetic unit for determining the position of the object over the light
source from the data of cameras or light sensors/image sensors.

4. Method according to claim 1, wherein the geometrical arrangement of
the cameras or light sensors/image sensors is form so that it make
possible a precision determining the position and the orientation of the
object.

5. Method according to claim 1, wherein the mount of multiple light
sources on the object that it make possible a precision determining the
orientation of the object.

6. Method according to claim 1, wherein the bandwidth of the light source
(2; 13; 22) and the bandwidth of the optical band-pass filter (3; 15; 23;
30) is attuned to each other.

7. Control device for a power wrench (38) to monitor the sequence of
tightening screw joints (40;41) and to control that each screw joint (40;
41) tighten with the right parameters, comprising: a position sensing
system (34-37; 39) which method is described in claims 1 to 9 is applied
to indicate continuously the actual position of the power wrench (38)
during tightening of screw joints (40; 41) on the component (42) to be
assembled; a arithmetic unit/control unit (44) of the position sensing
system (34-37; 39) for calculate the position of the power wrench (38)
and for control the tightening of the screw joints (40; 41), the
arithmetic unit/control unit (44) communicate with the control unit (45)
of the power wrench (38) to monitor the position of the power wrench (38)
and to monitor the tightening of the screw joints (40; 41); said control
units (44; 45) indicate an OK (o.k.) for each acceptable tightened screw
joint and indicate a NOK (not o.k.) for unacceptable tightening screw
joint.

8. Control device according to claim 7, wherein the said position sensing
system comprises one or more light sources (39) located on the power
wrench (38), and one or more cameras (34; 35) with optical band-pass
filters (36; 37) connected to the arithmetic unit/control unit (44) and
arranged to communicate with said control unit (45) of the power wrench
(38).

Description:

BACKGROUND OF THE INVENTION

[0001] The invention relates to a method and device for determine the
position of an object. The exact determining the position of objects in
the industrial production is a vary useful and necessary condition. The
acknowledgment the coordinates of the tools and components provide
increasing quality of products and decreasing production costs. For
example at tightening joint screws of cylinder head must follow the right
sequence to avoid stress in the cylinder head and clamp the cylinder head
seal uniformly. A screw joint which has not been acceptably tightened can
cause a break down of safety critical parts of a motor car.

[0002] At the moment there are several possibilities to determine the
position of an object:

[0003] Mechanical, for example through turn sensors or distance sensors.
The object is mounted on a movable arm. The Disadvantage of this system
is that a movable arm is fixed on a device and the freedom of movement is
limited.

[0004] Position determination through delay time, for example Global
Positioning System or ultrasound. The disadvantage of a system based on
radiowave is bad accuracy (circa 50 cm) and therefore is not sufficient.
A ultrasound positioning system is disturbed by sound of pneumatic
machines that are used in a production.

[0005] Position determination through a optical method with a camera. The
camera searches for a pattern or an object that is deposited in the
memory of the system.

[0006] This system is very disturbed for example by bad contrast, bad
lightening and radiation of other light sources.

[0007] It is an object of the invention to provide a method and device for
determining the position of an object precise and undisturbed. It
increase the quality on objects assembled by screw joints through force
the operator for removal an unacceptable tightened screw joint before he
move to the next screw joint or object.

[0008] Further objects and advantages of the invention will appear from
the following specifications and claims.

[0009] A preferred embodiment of the invention is described below with
references to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] FIG. 1 shows a schematic view of an object with a light source
which position will determine through a light sensor/image sensor with an
optical band-pass filter and an optical lens.

[0011]FIG. 2 shows a schematic 3D plane view of an object with a light
source and the light sensor/image sensor, the optical band-pass filter
and the optical lens are shown as a plane.

[0012] FIG. 3 shows a similar view as FIG. 2 but illustrates two systems
comprises light sensor/image sensor, optical band-pass filter and optical
lens as a plane for determining the position of the object in space.

[0013]FIG. 4 shows a schematic view of a workpiece carrier carrying an
object with screw joints to be tightened by a power wrench with position
indicating means.

DETAILED DESCRIPTION

[0014] The schematic arrangement shown in FIG. 1 comprises an object 1
with a light source 2, an optical band-pass filter 3, an optical lens 4,
a light sensor/image sensor 5, a front view of the light sensor/image
sensor 9, a pixel 10 on the light sensor/image sensor, a light beam 6
from the light source and a light beam 7 from other light source that is
unwanted. Number 8 shows the side view of the optical band-pass filter 3,
optical lens 4 and the light sensor/image sensor 5.

[0015] The arrangement in FIG. 1 describes the method of the invention for
sense the light from the light source 2 to determine the position of the
object 1. The light beam 6 from the object 1 passes the optical band-pass
filter 3, the optical lens 4 and meets the light sensor/image sensor 9.
The pixel 10 that is illuminated from the light beam 6 appear as a bright
pixel. All pixels that are illuminated from the light beam 6 together add
up to a bright flaw. The unwanted light beam 7 can not pass the optical
band-pass filter and therefore comes the bright flaw 10 on the light
sensor/image sensor only from the light source 2 from the object 1. The
bandwidth of the light source 2 and the bandwidth of the optical
band-pass filter 3 is attuned to each other.

[0016] In FIG. 2 there is illustrated the schematic arrangement in form of
planes.

[0017] The arrangement in FIG. 2 comprises an object 12 with a light
source 13, a plane 11 of the object 12, an optical band-pass filter 15,
an optical lens 16, a light sensor/image sensor 17, a pixel 18 on the
light sensor/image sensor 17, a light beam 14 from the light source 13
and a light beam 20 from other light source 19 that is unwanted.

[0018] The arrangement in FIG. 2 describes the method of the invention for
sense the light from the light source 13 to determine the position of the
object 12. The light beam 14 from the light source 13 passes the optical
band-pass filter 15, the optical lens 16 and meets the light sensor/image
sensor 17. The pixel 18 that is illuminated from the light beam 14 appear
as a bright pixel. All pixels that are illuminated from the light beam 14
together add up to a bright flaw. The unwanted light beam 20 can not pass
the optical band-pass filter 15 and therefore comes the bright flaw on
the light sensor/image sensor 17 only from the light source 13 on the
object 12. The bandwidth of the light source 13 and the bandwidth of the
optical band-pass filter 15 is attuned to each other.

[0019] In FIG. 3 there is illustrated the schematic arrangement in form of
planes which comprises two systems for determine the position of an
object in space.

[0021] The arrangement in FIG. 3 describes the method of the invention for
sense the light from the light source 22 to determine the position of the
object 21 in space. The light beam 46, 47 from the light source 22 passes
the optical band-pass filter 23, 30, the optical lens 24, 31 and meets
the light sensor/image sensor 25, 32. The pixel 27, 33 that is
illuminated from the light beam 46, 47 appear as a bright pixel. All
pixels that are illuminate from the light beam 46, 47 together add up to
a bright flaw. The unwanted light beam 48,49 can not pass the optical
band-pass filter 23, 30 and therefore comes the bright flaw on the light
sensor/image sensor 25, 32 only from the light source 22 on the object
21. The bandwidth of the light source 22 and the bandwidth of the optical
band-pass filter 23, 30 is attuned to each other. Under consideration of
geometrical context it is possible from the information of the light
sensor/image sensor 25, 32 to determine/calculate the position of the
object 21 in space.

[0022] In FIG. 4 there is illustrated an embodiment of the invention that
provides a device to control a power wrench 38 that each screw joint
40,41 is tightened with the right parameters. The power wrench 38 is
provided with an identity providing means in the form of a light source
39 which is recognised by two stationary position scanning cameras 34, 35
with optical band-pass filter 36, 37, wherein the light source 39, the
cameras 34,35, the optical band-pass filters 36, 37 and control
unit/calculation unit 44 form a position sensing system. The cameras
34,35 with the optical band-pass filter 36,37 are connected to the
control unit/calculation unit 44 and arranged to transfer the signals for
calculation the actual position of the power wrench 38. The control
unit/calculation unit 44 is connected to the control unit 45 of the power
wrench 38 and they communicate with each other.

[0023] The position sensing system is arranged to indicate continuously
the position of the power wrench 38 during operations on the workpiece 42
that lies on the workpiece carrier 43.

[0024] The control unit 45 of the power wrench 38 is programmed with
target torque levels, angle and/or spend time as well as limit value for
each tightening operation for each screw joint 40, 41. The control
unit/calculation unit 44 is programmed with the right sequence of
tightening screw joints 40, 41. That means that each tightening operation
will monitor by the control unit 45 and control unit/calculation unit 44
and they together will provide an OK or NOK indicating telling whether
the tightening result of each screw joints 40,41 is acceptable or not.

[0025] If a non-acceptable tightening result is occurred it is possible to
program the control unit 45 of the power wrench 38 so, that for example
the power wrench 38 can be locked until the non-acceptable tightening
screw joint is corrected before moving to the next screw joint or to the
next workpiece. Other possibilities for programming the control unit 45
are thinkable and are not limited after a non-acceptable tightening screw
joint.

[0026] An important advantage provided by the method and device according
to the invention is that no-preprogramming of screw joint positions is
necessary.

[0027] It is to be observed that the embodiment of the invention are not
limited to the above described examples but may be freely varied within
the scope of the claims. For instance, the above mentioned method to
communicate signals by wire between the control unit of the power wrench
and the control unit/calculation unit of the position sensing system may
be carried out by any available communication system and by wireless
communication too. All communications by wire can replace through
wireless communications. The control unit of the power wrench and the
control unit/calculation unit of the position sensing system can be
integrated to one control unit.

Patent applications in class AUTOMATIC CONTROL OF POWER OPERATED MEANS

Patent applications in all subclasses AUTOMATIC CONTROL OF POWER OPERATED MEANS